1. Field of Invention
The present invention relates to a preparation method for vinyl chloride, particularly relates to a method for preparing vinyl chloride with acetylene and dichlorethane.
2. Description of Related Arts
Polyvinyl chloride (PVC) is one of the most popular five kinds of plastic, with its production next only to polyethylene (PE), and ranks second plastics production of the world, with an annual production over 40 million tons.
The earliest synthetic method for polyvinyl chloride is acetylene method, i.e., under the catalysis of mercuric chloride, vinyl chloride is synthesized by the addition of acetylene and hydrogen chloride, and further polyvinyl chloride is polymerized by vinyl chlorides. Since mercuric chloride is adopted as a catalyst in this method, there will be serious mercury pollution problem. After the maturity of process for preparing ethylene by petroleum cracking, ethylene method is used to prepare vinyl chloride abroad, and the preparation process of vinyl chloride by the acetylene method had been basically obsoleted since the early 80s. In china, due to the shortage of ethylene resource and the abundance of calcium carbide resource, the production of PVC is still acetylene method-based. However, as the production of acetylene method keeps increasing, it will face with a huge pressure of environmental pollution. Recently, domestic counterparts have committed to the study of a mercury-free catalyst, and have made some achievements.
A Chinese patent application, application No. 201010149180.1, has provided a new preparation method for vinyl chloride, in which method, by taking barium chloride as a catalyst, vinyl chloride is prepared by a catalytic reforming of acetylene dichloroethane, such that opened up a new approach for mercury-free catalyst.
A Chinese patent application, application No. 201110330158.1 (international patent application No.: PCT/CN2011/081317) has provided a preparation method for a catalyst of vinyl chloride prepared by acetylene dichloroethane, and the performance of the catalyst prepared by such method is greatly improved, and basically meets the requirement of industrial production.
During the preparation of vinyl chloride by the catalytic reforming of acetylene dichloroethane, since the addition reaction of acetylene and hydrogen chloride is an exothermic reaction, and dehydrochlorination of dichloroethane is an endothermic reaction, when coupling the two reactions together, a micro exothermic reaction is formed, and the thermal effect of the reaction is not large, so that the reactor may adopt an adiabatic reactor; by a manner of inter cold shock, the reaction temperature may be controlled within a proper range, such that the reactor structure is greatly simplified.
Meanwhile, during the preparation of vinyl chloride by the catalytic reforming of acetylene dichloroethane, there will be some byproduct of hydrogen chloride. Since hydrogen chloride enables to decrease the starting temperature of the catalytic reforming of acetylene dichloroethane, accelerate the reaction velocity, as well as to inhibit a further increase of the concentration of hydrogen chloride in reaction system, thus after separation and recycling, the byproduct of hydrogen chloride feeds in with the acetylene dichloroethane, thereby greatly reducing the feed temperature, as well as helping to extend the service life of catalyst. Moreover, due to constraints of chemical equilibrium, it is impossible to entirely complete the preparation process of vinyl chloride by the catalytic reforming of acetylene dichloroethane at one time, but generally, with a conversion rate just about 80%, thus a separation and recycling performed on the reactant are needed.